It is desirable when providing means for lifting and lowering a vehicle window, to provide a mechanism which is as simple as possible, thereby providing a mechanism which is inexpensive to produce and mechanically effective. A primary criteria for mechanical effectiveness is that the window start and stop smoothly, without jerking or becoming stuck. Some of the vehicle window regulators which have been disclosed, may be broadly grouped in distinct categories:
A. Rack & Pinion
U.S. Pat. No. 4,389,818 to "Sakamoto" discloses a window regulating mechanism driven by an electric motor which is attached by a bracket to the bottom portion of a vehicle window. The output shaft of the motor drives a pinion (or sprocket), and is generally horizontally oriented. A single flexible plastic strap having teeth (or perforations) for engagement with a pinion or sprocket, is secured to a body panel and extends in a direction corresponding to the direction of movement of the window glass panel (generally vertical). The pinion of the output shaft drivingly engages the teeth of the flexible plastic strap--rotation of the pinion may thereby either lift or lower the window depending upon the direction of rotation of the output shaft.
U.S. Pat. No. 4,170,847 to "Pickles" discloses a window regulating mechanism of the "rack and pinion" type, wherein a vertically movable window at its lower edge is connected to a pair of transmission assemblies which are engageable with a pair of vertically oriented racks. The racks are horizontally spaced apart and each rack is proximate one side of the window. An electric motor attached to the window is movable therewith and has an output shaft having two pinions which synchronously engage the two racks for vertical movement.
B. Bowden Cable Systems
Many mechanisms have been disclosed in which bowden cables transfer tension or compression to move a window along a guide. Generally the drive means is stationary and moves a cable threaded inside a sheath to transmit tension and compression. The end of the cable may be attached to a shoe which is fixed to a window. Usually the shoe is guided by a single track for vertically lifting and lowering the window. Examples of "bowden cable" mechanisms may be seen in U.S. Pat. No. 4,483,100; 4,367,660; 4,211,122; 4,433,508; 3,831,320; 4,090,329; 4,199,899 and 4,237,656.
C. Closed Loop Cable Systems
Closed loop cable systems generally provided for the circulation of a cable by engaging the cable with a rotatable drum. A portion of the cable extends in a direction generally corresponding to the intended direction of movement for lifting and lowering the window. Usually a fitting is clasped to the cable and is guided for movement by a single track. The fitting is attached to the bottom of the window. Circulation of the cable may thereby either lift or lower the window depending upon the direction in which the cable is being circulated. Examples of such an arrangement may be seen in United Kingdom Patents Nos. 2,029,895; 2,022,683 and 2,029,502; and in U.S. Pat. Nos. 4,235,046; 4,480,409; 4,534,233; 4,110,935 and 4,440,354. In each of the foregoing examples a single track is employed as a means for guiding the fitting attached to the cable entraining the window for lifting and lowering. The art specifically addresses the problem of properly tensioning the cable so as to provide for a smooth transfer of force to the window. For example U.K. Patent No. 2,029,895 discloses a cable in a circulating loop wherein opposite ends of the cable are each connected by springs to a fitting joining the opposite ends in a loop so as to keep the cable constantly stretched. Other patents disclose a drum for engaging and winding a cable, wherein the drum has resilient biasing means or the like for maintaining tension in the cable and removing slack therefrom--for example U.S. Pat. Nos. 4,191,060 and 4,428,542; and, Canadian Patent No. 955,289.
D. Open Cable Systems
Open cable systems generally have a drum mounted on a door panel for engaging a cable. At least one end of the cable is attached by a fitting to the bottom portion of a window. A portion of the cable may pass over pulley guide means spaced above the bottom of the window thereby providing a mechanical advantage for lifting and lowering the window. For example U.S. Pat. No. 4,001,971 discloses a pair of cables engaging a rotatable drum mounted on a door panel. Each cable is attached at one end to a mount on the bottom of the window, at one side thereof; each cable passes over a first pulley supported vertically above each mount on the bottom of the window; each cable winds around the drum and passes under a pulley mounted proximate the floor of the door panel and horizontally opposite the first pulley; the said opposite end of each cable is attached to the underside of a mount on the bottom of the window. Accordingly, shortening the cable on one side will cause the opposite side of the cable to lengthen. The two cables allow for lifting both sides of the window. Each one of a pair of vertically extending horizontally spaced apart rods passes through a hole in one of the pair of window mounts for guiding the lateral movement of the window.
In another example German Patent No. 2,906,424 discloses a cable window regulator having a torsion winding mechanism. A pair of cables are each, at one end, wound onto drums at the opposite ends of a rod. The rod is housed coaxially in a sheath and engages the sheath housing by torsional springs for resilently biasing the cables.
It is therefore an object of the invention to provide an improved cable window regulator that is simple, effective and economical.
It is a further object of this invention to provide a cable window regulator having improved drive means for uniformly distributing the load when lifting and lowering a vehicle window and which starts and stops smoothly without jerking.
It is a further object of this invention to provide cable drive means suitable for lifting and lowering a vehicle window having a convex curvature.
Further and other objects of the invention will be apparent to those skilled in the art from the following Summary of Invention and detailed description thereof.